Interleukin-1 (IL-1) is a polypeptide produced by human cells that has pleiotropic biological effects and is involved in inflammation, immunologic challenges, and the response to infections. The genes for two different forms of IL-1, IL-1 alpha and IL-1 beta, have been cloned allowing production of large quantities of these cytokines by genetic engineering. IL-1 alpha is membrane bound in vivo and is biologically active. Specifically, in animal studies, IL-1 alpha has been shown to have immunoenhancing, bone marrow restorative and direct anti-tumor effects. Because of these effects, it is likely that IL-1 alpha will have significant clinical utility in the treatment of malignant disease and a phase I study of its toxicity and hematological and immunologic effects in humans is currently underway. Specifically, I will be looking at pre- and post-treatment bone marrow aspirates and peripheral blood smears in patients with metastatic malignant disease given increasing doses of IL-1 alpha.